NMR properties (chemical shift and relaxation rate) of acceptor and hydrogen bridge nuclei in hydrogen-bonded complexes

The NMR properties related to the formation of hydrogen bonds (HB) between phenol or N-methyltrifluoroacetamide and several acceptors (amines, carbony l compounds, nitriles, amides) in CCl4 or CHCl3 were investigated through t he analysis of NMR chemical shifts and relaxation times of the deuteron bri dge (H-2), and the chemical shifts of the heteronuclei (N-14 and O-17) dire ctly involved in the HB interaction. Thus, a comparison is made between suc h delta or T-1 values and nuclear shieldings or electric field gradients ca lculated by ab initio and DFT methods for the acceptor molecules, both isol ated and in 1:1 or 2:1 H-bonded complexes. The H-2 relaxation rates undergo small changes, essentially insensitive to the nature of the acceptor. On t he other hand, good relationships are found to hold between calculated and experimental chemical shift changes, both for H-2 and for the acceptor nucl ei. Copyright (C) 2001 John Wiley & Sons, Ltd.